Incoherent scattering from dielectric metasurfaces under the influence of electromagnetic eigenmodes.

Anomalous optical properties of microscopically inhomogeneous dielectric films placed on a thick metal sublayer are investigated. We study the reflection, scattering, and absorption of the coherent electromagnetic radiation as a function of the incidence angle. Computer simulations show the existence of the incidence angle of the laser beam when the scattering and absorption increase simultaneously for the s-polarization so that almost 60% of the incident light goes in the scattering channel. The critical angle corresponds to the excitation of Fabry-Perot mode. The effect makes it possible to manipulate the reflection from the metafilms.

Comparative evaluation of the depth of collagen and hyaluronic acid hydrolysis in vitro by collagenase and hyaluronidase preparations.

The molecular weights of collagen and hyaluronic acid solutions after their incubation with collagenase and hyaluronidase were evaluated by capillary viscosimetry. The results indicate high amylolytic activity of collagenase and the absence of proteolytic activity in hyaluronidase in an in vitro system.

Temperature and flow-velocity measurements by use of laser-induced electrostrictive gratings.

Light scattering from laser-induced electrostrictive gratings has been used for simultaneous, instantaneous, nonintrusive, and remote measurements of temperature and velocity in a submerged air jet. We accomplished phase-sensitive detection of scattered light by superimposing two signal beams whose frequencies were Doppler shifted by the movement of the grating. Temperatures in the range 295-600 K and flow velocities in the range 10-100 m/s were measured.

Generation and temporally resolved detection of laser-induced gratings by a single, pulsed Nd:YAG laser.

The infrared radiation of a pulsed Nd:YAG laser is employed to generate, either by electrostriction or by thermalization of absorbed laser energy, a spatially periodic density grating that oscillates in time. The second-harmonic output of the same laser is injected into a high-reflectance optical cavity, and the pulse trapped in the cavity is used to monitor the temporal evolution of the grating diffraction efficiency. The oscillation period of the diffraction efficiency depends on the sound velocity in the medium. If the gas composition is known, measurement of the sound velocity allows the temperature to be deduced. On the other hand, if the temperature is known, concentrations in isothermal binary mixtures can be determined. We demonstrate the applicability of this novel one-laser grating arrangement by concentration measurements in a cell containing methane-nitrogen mixtures and by preliminary temperature measurements in a premixed methane-air flame.

Laser-induced gratings in the gas phase excited by Raman-active transitions.

We report on a new time-resolved coherent Raman technique that is based on the generation of thermal gratings following a population change among molecular levels that is induced by stimulated Raman pumping. This is achieved by use of spatially and temporally overlapping intensity interference patterns generated independently by two lasers. When this technique is used in carbon dioxide, making use of transitions that belong to the Q branches of the v(1)/2v Fermi dyad, it is possible to investigate molecular energy transfer processes. A further unique feature of this method is spectral resolution that is better than that achieved by coherent anti-Stokes Raman scattering.

[Clinical fluorescent diagnosis of tumors using photosensitizer photogem]. / Klinicheskaia fliuorestsentnaia diagnostika opukholei s fotosensibilizatorom fotogemom.

During clinical trials of photodynamic therapy (PDT) the tissue fluorescence spectra under 510 nm laser excitation were recorded in 22 patients with tumors of the lungs, larynx, skin, gastric and esophageal carcinoma, and cancer of the gynecological organs before (autofluorescence) and after drug administration. A spectroscopic fluorescence detection system, developed at the General Physics Institute, Russian Academy of Sciences, was applied for tumor diagnostics. The system has been used for clinical fluorescence diagnostics with the aid of HPD-type photosensitizer Photogem (Moscow Institute of High Chemical Technologies) marked by selective retention in malignant tumors. Methods and equipment for spectra analysis aimed at estimating drug distribution in the near-surface layers of tissues, determining the tumor boundaries before photodynamic treatment, as well as studying drug pharmaco kinetics have been developed and tested. The results demonstrate the possibility of tumor detection by fluorescence even in low selectivity of drug accumulation which appears to be dependent on the stage and type of the disease and the organ involved.